Production of basic linear polymers



Patented a. 4, 1949 2,483,513 PRODUCTION OF BASIC LINEAR POLYMERS SidneyJames Allen and James England,

Drewltt, London,

Gordon Napier assignors, by meme assignments, to Celanese' Corporationof America, a corporation of Delaware No Drawing.

This application is a continuation in part of application S. No. 591,408filed May 1, 1945.

This invention relates to improvements in the production of polymers,and is more particularly concerned with the production of polymerssuitable for the manufacture of filaments, films and plastic materials,and with the production of coating compositions, moulding powders,plastics, foils, films, sheets, filaments and other articles therefrom.

We have discovered that very valuable basic linear polymers may beobtained by condensing a dibasic carboxylic acid or its equivalent witha polyamine containing two primary amino groups and one or moresecondary amino groups, the reagents being used in substantiallyequimolecular proportions. It appears that the reactivity of the primaryamino groups of the polyamine is so marked as compared with that of thesecondary amino groups that the former can react while the latter remainunchanged. This observation is of very considerable importance since notonly does it open up a new field of monomeric reagents suitable for theproduction of linear polyamides but in addition it enables polyamides tobe produced which have very desirable basic properties. The inventioncomprises broadly, therefore, the production of linear polymers byreacting in substantially equimolecular proportions a dibasic carboxylicacid or its equivalent with 'a diamine containing two primary aminogroups and one or more secondary amino groups.

In a number of cases, as will be described more fully below, bycontinuing the condensation, the linear polymer first obtained can bechanged into an insoluble or cross-linked polymer. These basic insolublepolymers, while not of value for the production of filaments, films andthe like, as referred to above, nevertheless have value, for example inabsorbingthe acid radicle from aqueous liquors containing salts, acidsor the like.

While such polyamines as diethylene triamine, triethylene tetramine,tetraethylene pentamine and LB-bis-B-aminoethyl amino hexane dia m i n eNH2CH2CH2NH(CH2) eNHCI-IzCHzNI-Iz, may be used for the purpose of thepresent invention, we prefer to use polyamines in which the primaryamino groups are separated by more than two, and preferably more thanthree, atoms from the secondaryamino groups in the same molecule. Bodiesof this type include dihexylene triamine (prepared from excess ofhexamethylene diamine and phthalirnidohexyl chloride),1.2-bisw-aminohexyl-amino-ethane and similar polyamines prepared by anyof the methods referred Application April 19,

In Great Britain April 12, 1944 6; (Claims. (Cl. 260-78) 1946, Serial tobelow. 4.4-diamino-diphenylamine is a further example of a suitablepolyamine. The following methods are available for forming polyaminessuitable for the present invention.

(a) One very suitable method consists in reacting an ova-paraffindihalide, for example ethylene dibromide, 1.4-dibrombutane,'1.6-dibromhexane and the like, with an excess, and preferably a veryconsiderableexcess, such as 20 moles, of an a-w-diamino-paraffin, forexample tetramethylene diamine, pentamethylene diamine, hexamethylenediamine and the like.

(b) Similarly an aminonitrile in excess may be reacted withanm-w-paraifin 'dihalide, and the resulting diamino-dinitrile may then bereduced by standard methods to the tetramine. Convenient reagentsinclude 6-amlno-capronitrile on the one hand and the parafiin dihalidesmentioned above on the other hand.

(0) Again, a halogen nitrile in excess may be reacted with ana-w-diamino-paraflin, and the resulting dinitrile again reduced to thetetramine. Suitable diamines are those mentioned under (a) above, whileas halogen nitriles we may use 7- brom-heptano-nitrile,G-chlor-capronitrile and 4-chloror brom-butyro-nitrile.

(d) The same type of tetramine may be formed by addition of two moles ofacrylonitrile or methacrylonitrile to an a-w-diamino-parafiin, followedby reduction of the resulting alkylene bisiimino-propionitrile oralkylene bis-B-isobutyronitrile.

(e) Lastly, a-w-paraflin dihalides, for instance those mentioned under(a) above, may be condensed With two moles of a' mono-acidylateddiamine, for example mono-acetyl hexamethylene diamine, and theresulting compound treated to split oil the acidyl groups. Themono-acidylated diamine should be used in considerable excess.

The dibasic carboxylic acids may be used in the free state or in theform of an ester, halide or amide, or, if water is present, as thenitrlle. suitable reagents include oxalic acid or its esters, halides oramide, urea, urethanes or dialkyl or diaryl carbonates, and thefollowing dicarboxylic acids or their equivalents: adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid and the like. It is notnecessary to use a dibasic acid in which the two acid groups are unitedsolely by carbon atoms, and the invention includes dibasic acids inwhich the acid groups are united by a chain containing non-reactiveatoms other than carbon, including oxygen, sulphur and tertiarynitrogen, as for example in diglycollic acid,

3 thiodiglycollic acid and N-methyl-imino-diacetic acid andN-methyl-imino-dipropionic acid.

The invenion further includes using the above polymer-forming reagentstogether with other linear polyamide-iorming reagents, for examplediamines with dicarboxylic acids or mono-aminomonocarboxylic acids. Forexample we may use a mixture of a polyamine of the: type described, adiprimary amine and a dicarboxylic acid. In calculating the proportionsof reagents to be used, one molecule of combined polyamine and diamineshould be condensed with substantially one molecule of dicarboxylicacid. In other words, the carboxylic acid groups present in the mixtureshould be substantially equivalent to the primary amino groups presentin the mixture. In all forms of the invention, the proportion ofdicarboxylic acid falls substantially short of that which is equivalentto the primary and secondary amino groups combined.

The best polymers are those produced by condensation of a dibasiccarboxylic acid or its equivalent with a polyamine containing twoprimary amino groups and one or two secondary amino groups. In thisseries of polymers, linear polymers are easily formed from oxalic esterand any of the polyamines previously mentioned, and indeed so far wehave not encountered a single case in which the polymerisation has ledto a cross-linked product. While the proportion of the polyamine shouldnot be substantially more than equimolecular to the oxalic ester, theproportion of the oxalic ester may be raised a little aboveequimolecular with regard to the polyamlne, say to above, withoutaffecting substantially the nature of the polymer obtained. With higheracids, for example adipic acid and its higher homologues as mentionedabove, the position is, however, different, Here continued heating ofthe dicarboxylic acid with the polyamine does result in cross-linkingand in the production of an insoluble polymer. In this case it isnecessary, where a linear polymer is required, to stop the condensationbefore this cross-linking sets in. We have found that this is not verydiflicult, and in many cases we can produce linear polymers whichrequire heating for several more hours before cross-linking occurs.

Normally in the production of polymers from bifunctional reagents, theintrinsic viscosity of the linear polymer appears to be a good index ofthe degree of polymerisation and of the ability of the polymer to formgood films or to form filaments. This also appears to be the case whenoxalic ester is condensed with polyamines of the type in which theprimary amino groups are separated from secondary amino groups by morethan three atoms. In other condensations covered by the presentinvention, however, and particularly those which use the higherdicarboxylic acids, there appears to be some anomaly about theviscosity, and in the result the viscosity is no longer a good index ofthe ability of the polymer to form filaments. This may be illustrated bythe case of condensing 1.S-bis-B-aminoethyl-aminohexane with adipicacid. It is found, for example, that if an equimolecular mixture ofthese two bodies be heated at 155 C. for 15 hours, the product, which isstill soluble in metacresol, has an intrinsic viscosity, measured as a1% solution in metacresol, of the order of 0.6-0.7. Normally a polymerhaving such a viscosity would already be filament-forming and thefilaments would be capable of being cold-drawn. With this polymer, thisis not the case, and at this stagethe ability to form fibres has not yetappeared. It is partly for this reason that we prefer to use polyaminesoi which the primary amino groups are separated by more than two, andpreferably more than three, atoms from the secondary amino groups.

In all the reactions discussed above in which condensations are carriedout between carboxylic and amino groups, the carboxylic groups may bereplaced by equivalent radicles, for example carboxylic ester groups,both alkyl and aryl esters, by carboxylic amide, by carboxylic halidegroups or by nitrile groups (together with water). Similarly aminogroups may be replaced by acidylamino groups containing acidyl radicleswhich are readily replaced, for example the formyl radicle. Further,instead of using compounds containing primary amino groups,corresponding compounds containing isocyano or isothiocyano groups maybe employed, the reaction with a carboxylic acid then involving theelimination of carbon dioxide or carbon oxysulphide instead of water.Condensations between amino, acidylamino, isocyano or isothiocyanogroups and carboxylic acid, carboxylic ester, carboxylic amide -obtain apolymer of sufiiciently high molecular weight to be fibre-forming. Insome cases, particularly when using oxalic ester, the initial stages ofthe condensation may be carried out at a temperature much lower than C.For example, the reaction of oxalic ester with diethylene triamine,triethylene tetramine and the like begins at room temperature. Where areagent is employed which is volatile at the temperature ofcondensation, the initial stages of the condensation may be carried outunder pressure or reflux so as to prevent the removal of such a volatilereagent from the sphere of action.

The condensation may be carried out with or without a diluent, in thelatter case preferably while melting the monomeric substances or the lowpolymers obtained after the condensation has been carried some way.Where a diluent is used, it is preferably a solvent for the resultingpolymer, for example a phenolic solvent such as phenol itself, thecresols and xylenols. Conveniently the solvent or diluent is so chosenthat it boils at the desired polymerisation temperature, so that thecondensation, at least in its initial stages, may be carried out atatmospheric pressure while boiling. Where a volatile body such as wateror ethyl alcohol is split off during the condensation, it is desirable,as the condensation proceeds, to apply vacuum or alternatively a currentof inert gas, so as to promote the condensation. It is sometimesdesirable to employ a condensation catalyst with a view to carrying outthe reaction at a lower temperature than would otherwise be possible. Avery small proportion of phosphoric acid, for example of the order of.01 to .1% of the reagents, is usually suflicient for this purpose. Toavoid discolouration, it is in all cases desirable to exclude air, sothat the condensation may, for example, be carried out in the presenceof oxygen-free nitrogen or other inert gas.

initial reaction can take place. Furthermore, it is preferable to havepresent during such an elimination of a hydrohalide acid a. reagentwhich will absorb or neutralise the acid, for examplean inorganic baseor a tertiary organic base.

The invention includes the production of filaments, films and otherarticles from the polymers produced as described above. In formingfilaments, the choice of the method of spinning depends in part on theproperties of the polymers. Where solutions in organic solvents canreadily be produced, dry spinning methods may be employed with solutionsin volatile solvents, and wet spinning methods with solutions involatile or even comparatively non-volatile solvents. Polymers having abasic character may be wet spun from acid solution. The polymers can bespun by melt spinning methods, 1. e. by extruding a melt of the polymerthrough suitable orifices. In

general the temperature of the polymer to be extruded should be some10-30 above the melting point of the polymer. This melting temperaturemay be modified to some extent by mixing the polymer with suitableproportions of plasti- 4 cisers, for example sulphonamide plasticisers,phenolic plasticisers, urea and thiourea plasticisers and the like. Suchplasticisers may either be left in the products or may be partially orcompletely extracted therefrom.

The filaments, if formed from a polymer of sufficiently high molecularweight, may be drawn out at comparatively low temperatures, or even atatmospheric temperature, to very fine filaments having high tenacity andgood elasticity. The

resulting filaments may then be used for any of the purposes to whichartificial silks have in the past been applied.

While the invention is especially directed to the manufacture andapplication of fibre-forming polymers, it is not limited thereto andembraces the production of similar linear polymers suitable, forexample, for use as softening agents, coatings, film-forming substances,and the like, and as already referred to, includes the continuation ofthe condensation to produce basic insoluble polymers. Moreover, for theabove applications, the linear polymers of the present invention may bemixed with other fibre-forming, film-forming or lacquer substances orother ingredients, for example cellulose acetate, acetobutyrate,butyrate and aceto-stearate, ethyl cellulose, oxyethyl cellulose,oxyethyl cellulose acetate, benzyl cellulose and other cellulosederivative, plasticisers or softening agents, dyestuffs, pigments andthe like.

The polymers being basic in character have a good affinity for acid wooldyes, so that filaments, and yarns and fabrics containing them, as wellas other articles containing the polymers may readily be dyed orotherwise coloured with such dyestuffs.

The polymers, especially in the form of filaments or other structures orin any other form, may be after-treated by means of various reagentswith the object of changing their properties, for instance increasingthe melting point and/or making them insoluble in organic solvents. Thesecondary amino groups disposed along the polymer chain are particularlyuseful for this purpose. Thus, for instance, the polymers may be treatedwith formaldehyde or other aldehyde, with a mono-, dior poly-basic acidsaturated or unsaturated or its equivalent, such as the acid chloride,with sulphuryl chloride, acrylonitrile, acrylic ester, carbondisulphide, a

di-iso'cyanate, especially an alkylene di-isocyanate, an alkylenedihalide or the like.

The following examples illustrate the invention but are not to beconsidered as limiting it in any way. It should be noted that in theexamples dealing with the production of polymers the precise degree ofreaction, and hence the intrinsic viscosity and molecular weight, dependupon a number of factors, for example the temperature, the pressure, theratio of surface to volume, the rate of flow of inert gas through thesystem and the general design of the apparatus in so far as this affectsthe ease with which volatile by-products of the polymerisation reactionare eliminated. Accordingly the details given in these examples can onlybe taken as a general guide to the manner in which the invention can becarried out.

Examms 1 Preparation of izz-bis-w-aminohezylaminoethane 18.8 parts ofethylene dibromide in 40 parts of 95% ethanol were added to a mixture of232 parts of hexamethylene diamine and 150 parts of 95% ethanol at 80-90C., and the mixture held at this temperature for 3 hours, care beingtaken to avoid access of atmospheric carbon dioxide. To the cold mixturewas added 11.2 parts of caustic potash in parts of 95% ethanol and theprecipitated potassium bromide was filtered oil. The alcohol was removedfrom the filtrate by distillation at 50 mms., and most of the excessdiamine recovered by distilling at 20 mms. Distillation was thencontinued at a pressure between 05 and 5 mms. and gave a fore-runconsisting of hexamethylene diamine (boiling about /1 mm.) and a goodyield of 1 :2-bis-w-amino hexylamino-ethane hydrate as a fractionboiling about.175/0.5. This fraction set to an almost colourless solid.The tetramine hydrate, which contained 1-2 moles of water according tothe precise conditions of the distillation, could be recrystallised frompetrol ether or from a small amount of water. The dihydrate had m.70.Prolonged heating of the hydrate under air condensed reflux at 200/1 mm,followed by vaccum distillation, gives the substantially anhydrous base,but it is not necessary to isolate the material in this form for thecondensation.

The amine formed a tetra-benzene-sulphonyl derivative M. P. 168 and aderivative with 3 moles of benzaldehyde, 1:3-bis(G-benzylideneamino-hexyD-2-phenyl tetrahydro imidazole M. P.

EXAMPLE 2 Condensation of 1:Z-bis-W-aminohexylamino) ethane with adipicacid 7.3 parts of adipic acid (1 molecular proportion) and 15.4 parts oftetramine hydrate (containing 12.9 parts, 1 molecular proportion of puretetramine) were mixed in 8 parts of methanol.

The methanol was removed by heating in a melt gave pliable fibres withcold-drawing properties. Elementary analysis of this polymer confirmedthe structure Much the same result was obtained by streetin: thepolymerisation throughout at 195-200 for 4 hours. On the other hand,further heating of the above polymers at 195-200 gave an infusible,tough cross-linked polymer, insoluble in but swollen by m-cresol andformic acid.

Similar products to the linear and cross-linked polymers mentioned abovewere obtained when adipic acid was replaced by s'uberic acid (M. Pt. oflinear polymer about 150) or sebacic acid (M. Pt. of linear polymerabout 145).

The presence of free secondray amino groups in the linearadipic/tetramine polymer was demonstrated by the formation of a nitrosoderivative by treatment with nitrous acid in dilute sulphuric acid. Thisnitroso derivative, an almost white, fibrous polymer, gave a strongLiebermann reaction and decomposed on heating from about 150 upwards.Unlike the original polymer it was insoluble in dilute hydrochloricacid.

EXAMPLE 3 Condensation of 1:2-bis-w-a1ninoherylaminoethane with ethyloxalate 13.8 parts of the tetramine monohydrate (1 molecular proportion)were dissolved in 120 parts of 95% ethanol, 7.3 parts of ethyl oxalate(1 molecular proportion) added, and the mixture refluxed for hours. Theethanol was then distilled ofi in a stream of hydrogen and the residueheated in a current of hydrogen at 165 for 2 hours. The polymericproduct remained as a hard, horny mass, somewhat resembling ivory. ItsI. V. (1% solution in m-cresol) was-about 0.3 and the M. P. about 140.It showed incipient fibre-forming properties.

Using the same procedure as above, but heating for hours at 165", withor without a further 3 hours at 180/1 mm., gave a polymer of I. V.0.5-0.6, M. Pt. about 150-5". This polymer was slowly soluble inm-cresol and rapidly soluble in formic acid. It readily formed pliablefibres with marked cold-drawing properties. Elementary analysis of thepolymer indicated the structure Polymers of much the same propertieswere obtained using 0.94 molecular proportions instead of the 1.0molecular proportion of tetramine, other conditions being the same.

The above polymer, intrinsic viscosity ca. 0.55-0.6, could be melt-spunsatisfactorily at a melt temperature of 170-5 using a spinneret havingan orifice of 0.15-0.25 mm. to form lustrous, pliable monofils with goodcold drawing properties.

EXAMPLE 4 Condensation of area with. 1:2-bis-(w-aminohexylamino)--ethane 2.78 parts tetramine hydrate (corresponding Condensation ofdi-herylene triamine with oxalic ester The dihexylene triamine for thiscondensation was prepared by one of the methods described in U. S.Application S. No. 672,329, filed May 25, 1946, namely by condensingphthalimidohexyl chloride with a very large excess of hexamethylenediamine, removing excess diamine hydrolysing the residue containing thephthalyl triamine and isolating the free base by distillation 13. Pt.155/ca. 0.2 mm. 2.15 parts (1 molecular proportion) of the triamine in10 parts of ethanol were mixed with 1.46 parts (1 molecular proportion)of ethyl oxalate in 8 parts of ethanol and the. mixture refluxed for 5hours in hydrogen. The ethanol was then distilled off and the residueheated in a current of hydrogen for 1 hour at 200 C. and 2 hours at 220.The resultant fibreforming polymer had M. Pt. ca. -195, was soluble inm-eresol and formic acid but insoluble in ethanol and acetone. Its waterresistance was better than that of the product ot-Example 3.

EXAMPLE 6 Condensation of di-hearylene triamine with suberic acid 2.15parts (1 molecular proportion) of the triamine in 10 parts of ethanolwere mixed with 1.74 parts (1 molecular proportion) of suberic acid in12 parts of ethanol. The solvent was distilled ofi and the residueheated in a current of hydrogen for 2 hours at to give an ivory-like,moderately hard polymer M. Pt. ISO-70, intrinsic viscosity (1% inm-cresol) ca. 0.45. soluble in formic acid and m-cresol, insoluble inacetone. After a further 0.5 hour at 195 the polymer was a hard,transparent glass, M. Pt. ca. soluble in formic acid. It gavecold-drawable fibres from the melt. Still further heating at the sametemperature gave an infusible, crosslinked, transparent glass, swollenby, but insoluble in, formic acid and m-cresol.

EXAMPLE '7 Mixed polymer from hexamethylene diamine,

ethyl oxalate and 1:2'-bis-(w-aminohea:ylamino) -e thane 2.76 parts oftetramine hydrate (corresponding to 2.58 parts, 0.5 molecular proportionof pure tetramine), and 1.16 parts of hexamethylene diamine (0.5molecular proportion) in 18 parts of ethanol were mixed with 2.92 partsof ethyl oxalate (1 molecular proportion). The mixture was refluxed for5 hours, the alcohol distilled 011 and the residue heated in a currentof hydrogen for 12 hours at 255 and 1 hour at 282. The resultant polymerhad M. Pt. ca 225, intrinsic viscosity (1% in m-cresol) ca. 0.4, wassoluble in m-cresol and formic acid and insoluble in acetone andethanol.

Exmru: 8 After-treatment of fibres The following treatments were allapplied to undrawn fibres obtained as in Example 3.

(a) Ethyl oxalate The fibre was heated with parts of ethyl oxalate for 1hour at 130 C., the excess oxalate decanted after cooling and the fibreswashed with acetone and dried. The weight increase was 20%. The treatedfibres had cold-drawing properties, did not fuse on holding at 200 for Iminute, fused partially after 1 minute at 250 and were of considerablyimproved resistance to boiling water.

(b) Carbon disulphide The fibre was refluxed in 10 parts carbondisulphide for 3 hours, excess disulphide decanted and the fibres thenheated in nitrogen at 100 for 2 hours and 130 for 0.5 hour. The weightincrease was about The treated fibres were of considerably enhancedresistance to boiling water and softened from 180 upwards.

(c) Ethyl carbonate The fibre was refluxed with 10 parts of ethylcarbonate for 6 hours, the reagent decanted hot and the fibre washedwith acetone and dried. The treated material fused only slightly, if atall, after 1 minute at 250.

Exlmru: 9 After-treatments of films with maleic acid where mis therelative viscosity of a solution of the polymer of the statedconcentration in metacresol, and c is the concentration of the solutionin grams per 100 cubic centimetres of solution.

In the appended claims, the dicarboxylic acid equivalents e. g. ester,halide or amide, and the amine equivalents, e. g. the formylamino group,are included in the phrase "amide-forming derivatives of the acid" or"the amine as the case may be.

Having described our invention, what we desire to secure by LettersPatent is:

1. Process for the production of basic linear polyamides, whichcomprises heat reacting a polyamine containing two and only two primaryamino groups and at least one secondary amino group and whose primaryamino groups are its sole reacting groups, the primary amino groupsbeing separated from each secondary amino groups present by at least 2atoms with a substantially equimolecular quantity of oxalic ester untila fiber-forming polymer is produced.

2. Process for the production of basic linear polyamides, whichcomprises heat reacting a polyamine containing two and only two primaryamino groups and at least one secondary amino group and whose primaryamino groups are its sole reacting groups, the primary amino groupsbeing separated from each secondary amino group present by at leastthree atoms, with a substantially equimolecular quantity of oxalic esteruntil a fiber-forming polymer is produced.

3. Process for the production of basic linear polyamides, whichcomprises heat reacting a tetramine of the formula where a: is more thanthree and whose primary amino groups are its sole reacting groups with asubstantially equimolecular quantity of oxalic ester until afiber-forming polymer is produced.

4. Process for the production of basic linear polyamides which comprisesheat reacting 1:2- bis-w-aminohexyl-amino-ethane with a substantiallyequimolecular quantity of oxalic ester and continuing the reaction untilthe fiber-forming polymer is produced.

5. A linear fiber-forming polymer obtained by the process of claim 1.

6. A linear fiber-forming polymer obtained by the process of claim 4.

SIDNEY JAMES ALLEN. JAMES GORDON NAPIER DREWI'I'I'.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,314,972 Dreyfus Mar. 30, 19432,325,567 Bock et a1. July 27, 1943 2,374,354 Kaplan Apr. 24, 1945

